In the simplest form filters are formed with combinations of resistors and capacitors, with the frequency characteristic of the filter being dependent upon the values of the resistors and capacitors. Integrated circuit component values are subject to variations as a result of processing tolerances and operating temperature. For example, integrated resistors can typically vary plus or minus 30% due to processing and an additional plus or minus 50% due to temperature variations.
Accordingly, the cutoff (or corner) frequency, f.sub.c, of the conventional integrated filter circuit tends to drift as the operating temperature of the semiconductor circuit changes.
Still another shortcoming of a conventional semiconductor integrated filter circuit is that its frequency corner is limited to frequencies above the audio range due to a limit on the amount of capacitance that can be obtained on an integrated circuit.